1. Field of the Invention
The present invention relates to a circulation filter mounting structure in a disk drive such as a magnetic disk drive or an optical disk drive.
2. Description of the Related Art
In general, a magnetic disk drive for a computer adopts a contact start and stop (CSS) system defining a relation between a magnetic head and a magnetic disk facing it. In this system, while the disk is being rotated, the head is kept flying from the disk at a microscopic height owing to the balance between a flying force applied to the head by an air flow generated by high-speed rotation of the disk and an elastic force of a spring arm pressing the head on the disk.
In such a magnetic disk drive, if dust is present inside the disk drive, the dust enters a gap between the magnetic head and the magnetic disk during rotation of the disk to cause read error or in the worst case, may cause head crash. To cope with this problem, the magnetic disk drive employs a breather filter for preventing entry of dust from the outside of the disk drive and a circulation filter for collecting dust generated inside the disk drive.
Referring to FIG. 7, there is shown a top plan view of a conventional magnetic disk drive having such a circulation filter under the condition where a cover (not shown) is removed. Reference numeral 12 denotes a housing (enclosure) composed of a base 14 and the cover. A spindle hub to be rotatably driven by an inner hub motor (not shown) is provided on the base 14. A plurality of magnetic disks 20 and spacers (not shown) are alternately stacked and mounted on the spindle hub. That is, the plurality of magnetic disks 20 are regularly spaced from each other and are fixedly mounted on the spindle hub by securing a disk clamp 18 to the spindle hub by screws.
Reference numeral 22 denotes a rotary head actuator composed of an actuator arm assembly 26 and a magnetic circuit 28. The actuator arm assembly 26 is rotatably mounted on a shaft 24 fixed to the base 14, and has a plurality of actuator arms 30 extending in one direction from the center of rotation. A spring arm 32 supporting a magnetic head 34 is fixed to one end portion of each actuator arm 30.
Reference numeral 36 denotes a flexible printed circuit sheet (FPC) for taking out a signal from each magnetic head 34. The flexible printed circuit sheet 36 is fixed at its one end to the actuator arms 30 and is connected at the other end to a connector 38. A circulation filter 40 is provided in the vicinity of the head actuator 22 where dust tends to be generated, so as to immediately collect the dust generated.. However, in such a conventional structure having the circulation filter 40 located at that position, an air flow generated by the rotation of the disks 20 is disturbed by the head actuator 22 located upstream of the circulation filter 40 in respect of the flowing direction of the air flow, and becomes stagnant before the filter 40. Accordingly, the dust cannot be efficiently filtered off by the filter 40. Further, as large spaces are present on the right and left sides of the filter 40, the air partially flows through these large spaces without being passed through the filter 40. Accordingly; the dust contained in the air flow is not filtered off by the filter 40.
Referring next to FIG. 8, there is shown another conventional magnetic disk drive which has seen increased use in recent years. The magnetic disk drive shown in FIG. 8 employs a circulation filter 40' located at a position opposite to the head actuator 22 with respect to the center of the magnetic disks 20. The circulation filter 40' is mounted in such a manner that the filter 40' is attached to a resin molding frame and the frame is fitted with the base 14 or the cover. Owing to this location of the circulation filter 40', an air flow generated by the rotation of the magnetic disks 20 steadily advances along the inner wall surface of the base 14 and is efficiently directed toward the circulation filter 40' as shown by an arrow A in FIG. 8. Accordingly, more dust can be collected per unit time in comparison with the prior art shown in FIG. 7.
However, yet in the prior art shown in FIG. 8, an air flow shown by an arrow B acts so as to reverse an air flow shown by an arrow C passing through the filter 40'. As a result, the air flow C passing through the filter 40' is decreased in quantity by a reverse flow component, thus reducing a dust collection efficiency..